Ascorbic acid and related compounds are of known utility in skin-lightening and other technologies related to hyper-pigmentation. Ascorbic acid formulations, however, are prone to oxidation and are easily destabilized. In addition, cosmetic or pharmacological compositions comprising these acids may damage tissue or irritate human skin on repeated topical applications due to lower pH of the formulations. Hence, ascorbic acid and other related compounds have been compounded with other hydrophobic materials to improve their stability and performance. Most recently, ester derivatives of ascorbic acid and 2-keto-acid saccharides have been disclosed in WO 2006/066227 wherein the ester is introduced by ester bond formation between at least one hydroxy-functionality on the ascorbic acid or 2-keto-acid saccharide and a carboxy-functional organosiloxane. The organosiloxane structures suggested in WO 2006/066227 are numerous. However, the working examples in WO 2006/066227 emphasized A-B-A structures based on a linear polydimethylsiloxane having end groups containing an ester linkage to ascorbic acid. While the examples in WO 2006/066227 demonstrated skin lightening effects and good formulation stabilities, they did not provide skin lightening effects equivalent or better than kojic acid. Kojic acid is known for its skin lightening capabilities and is often used as a benchmark for determining skin lightening performance. However, kojic acid's water solubility can limit its delivery and formulation latitude. Furthermore, the use of kojic acid in skin care formulation is questioned in some countries for safety reasons.
The present inventors have unexpectedly discovered certain short chain organosiloxanes containing ester derivatives of ascorbic acid provide enhanced skin lightening performance. In particular, these ascorbyl containing short chain organosiloxanes have skin lightening performance comparable to or better than kojic acid. Furthermore, the present ascorbyl containing short chain organosiloxanes are useful in many personal care formulations because of their compatibility with many organic oils and silicones.